Requires a copper cofactor and Ca2+. The enzyme, which is found in both prokaryotes and eukaryotes, catalyses a modification of a conserved L-cysteine residue in the active site of sulfatases, generating a unique 3-oxo-L-alanine residue that is essential for sulfatase activity. The exact nature of the thiol involved is still not clear - dithiothreitol and cysteamine are the most efficiently used thiols in vitro. Glutathione alo acts in vitro, but it is not known whether it is used in vivo.